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When a microwave filter consisting of vertical parallel metal rods is in the absorbing position, oscillating currents are set up in the rods. At any one instant, the current in each rod has the same magnitude and direction. At that instant


A) the rods will try to move apart horizontally.
B) the rods will try to move together horizontally.
C) the rods will try to shift vertically upwards.
D) the rods will try to shift vertically downwards.
E) the rods will not be affected because the source of current is not a battery.

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An ideal solenoid of radius a has n turns per unit length and current I. The magnetic flux ΦB through any area completely inside the solenoid, centered on the solenoid axis but at a 45° angle to the axis so that it touches the inside of the solenoid as shown below, is ​ An ideal solenoid of radius a has n turns per unit length and current I. The magnetic flux ΦB through any area completely inside the solenoid, centered on the solenoid axis but at a 45° angle to the axis so that it touches the inside of the solenoid as shown below, is ​ ​ A) . B) . C) μ0πa2nI. D) 2μ0πa2nI. E) 0. ​


A) An ideal solenoid of radius a has n turns per unit length and current I. The magnetic flux ΦB through any area completely inside the solenoid, centered on the solenoid axis but at a 45° angle to the axis so that it touches the inside of the solenoid as shown below, is ​ ​ A) . B) . C) μ0πa2nI. D) 2μ0πa2nI. E) 0. .
B) An ideal solenoid of radius a has n turns per unit length and current I. The magnetic flux ΦB through any area completely inside the solenoid, centered on the solenoid axis but at a 45° angle to the axis so that it touches the inside of the solenoid as shown below, is ​ ​ A) . B) . C) μ0πa2nI. D) 2μ0πa2nI. E) 0. .
C) μ0πa2nI.
D) 2μ0πa2nI.
E) 0.

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Two long straight wires carry currents perpendicular to the xy plane. One carries a current of 50 A and passes through the point x = 5.0 cm on the x axis. The second wire has a current of 80 A and passes through the point y = 4.0 cm on the y axis. What is the magnitude of the resulting magnetic field at the origin?


A) 200 μT
B) 600 μT
C) 450 μT
D) 300 μT
E) 400 μT

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Equal currents of magnitude I travel into the page in wires M and N. Eight directions are indicated by letters A through H. Equal currents of magnitude I travel into the page in wires M and N. Eight directions are indicated by letters A through H. The direction of the magnetic field at point P is A) B. B) C. C) D. D) E. E) F. The direction of the magnetic field at point P is


A) B.
B) C.
C) D.
D) E.
E) F.

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A solenoid consists of 100 circular turns of copper wire. Parts of three turns, A, B and C, are shown below. A solenoid consists of 100 circular turns of copper wire. Parts of three turns, A, B and C, are shown below. When a current flows through the coil, A) both A and C are repelled by B. B) A is attracted to B; C is repelled by B. C) neither A nor C is attracted to or repelled by B. D) A is repelled by B; C is attracted to B. E) both A and C are attracted to B. When a current flows through the coil,


A) both A and C are repelled by B.
B) A is attracted to B; C is repelled by B.
C) neither A nor C is attracted to or repelled by B.
D) A is repelled by B; C is attracted to B.
E) both A and C are attracted to B.

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A long solenoid (n = 1200 turns/m, radius = 2.0 cm) has a current of a 0.30 A in its winding. A long wire carrying a current of 20 A is parallel to and 1.0 cm from the axis of the solenoid. What is the magnitude of the resulting magnetic field at a point on the axis of the solenoid?


A) 0.60 mT
B) 0.85 mT
C) 52 μT
D) 0.40 mT
E) 0.75 mT

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Two solenoids are each made of 2000 turns of copper wire per meter. Solenoid I is 2 m long, while solenoid II is 1 m long. When equal currents are present in the two solenoids, the ratio of the magnetic field BI along the axis of solenoid I to the magnetic field BII along the axis of solenoid II, BI/BII, is


A) 1/4.
B) 1/2.
C) 1.
D) 2
E) 4.

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A toroid is made of 2000 turns of wire of radius 2.00 cm formed into a donut-shape of inner radius 10.0 cm and outer radius 14.0 cm. When a 30.0-A current is present in the toroid, the magnetic field at a distance of 11.0 cm from the center of the toroid is


A) 0.0857 T.
B) 0.109 T.
C) 0.120 T.
D) 0.600 T.
E) 0.685 T.

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Two long parallel wires carry unequal currents in the same direction. The ratio of the currents is 3 to 1. The magnitude of the magnetic field at a point in the plane of the wires and 10 cm from each wire is 4.0 μT. What is the larger of the two currents?


A) 5.3 A
B) 3.8 A
C) 4.5 A
D) 3.0 A
E) 0.5 A

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The figure shows a cross section of three parallel wires each carrying a current of 5.0 A out of the paper. If the distance R = 6.0 mm, what is the magnitude of the magnetic force on a 2.0-m length of any one of the wires? The figure shows a cross section of three parallel wires each carrying a current of 5.0 A out of the paper. If the distance R = 6.0 mm, what is the magnitude of the magnetic force on a 2.0-m length of any one of the wires? A) 2.5 mN B) 3.3 mN C) 2.2 mN D) 2.9 mN E) 1.7 mN


A) 2.5 mN
B) 3.3 mN
C) 2.2 mN
D) 2.9 mN
E) 1.7 mN

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Three long, straight, parallel wires each carry a current of 10 A in the positive x direction. If the distance between each wire and the other two is 10 cm, what is the magnitude of the magnetic force on a 20-cm length of either of the wires?


A) 57 μN
B) 40 μN
C) 69 μN
D) 50 μN
E) 20 μN

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A long wire lies in a tangle on the surface of a table, as shown below. When a current is run through the wire as shown, the largest component of the magnetic field at X points A long wire lies in a tangle on the surface of a table, as shown below. When a current is run through the wire as shown, the largest component of the magnetic field at X points A) into the table. B) out of the table. C) parallel to the nearest segment of wire. D) antiparallel to the nearest segment of wire. E) along a circle which has its center at the center of the overall loop.


A) into the table.
B) out of the table.
C) parallel to the nearest segment of wire.
D) antiparallel to the nearest segment of wire.
E) along a circle which has its center at the center of the overall loop.

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Two current loops are coaxial and coplanar. One has radius a and the other has radius 2a. Current 2I in the outer loop is parallel to current I in the inner loop. The magnitude of the magnetic field at the center of the two loops is


A) 0.
B) Two current loops are coaxial and coplanar. One has radius a and the other has radius 2a. Current 2I in the outer loop is parallel to current I in the inner loop. The magnitude of the magnetic field at the center of the two loops is A) 0. B) . C) . D) . E) . .
C) Two current loops are coaxial and coplanar. One has radius a and the other has radius 2a. Current 2I in the outer loop is parallel to current I in the inner loop. The magnitude of the magnetic field at the center of the two loops is A) 0. B) . C) . D) . E) . .
D) Two current loops are coaxial and coplanar. One has radius a and the other has radius 2a. Current 2I in the outer loop is parallel to current I in the inner loop. The magnitude of the magnetic field at the center of the two loops is A) 0. B) . C) . D) . E) . .
E) Two current loops are coaxial and coplanar. One has radius a and the other has radius 2a. Current 2I in the outer loop is parallel to current I in the inner loop. The magnitude of the magnetic field at the center of the two loops is A) 0. B) . C) . D) . E) . .

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An ideal solenoid of radius a has n turns per unit length and current I. The magnetic flux ΦB through any circular area of radius a inside the solenoid, centered on and perpendicular to the solenoid axis, is


A) An ideal solenoid of radius a has n turns per unit length and current I. The magnetic flux ΦB through any circular area of radius a inside the solenoid, centered on and perpendicular to the solenoid axis, is A) . B) . C) μ0πa2nI. D) 2μ0πa2nI. E) 0. .
B) An ideal solenoid of radius a has n turns per unit length and current I. The magnetic flux ΦB through any circular area of radius a inside the solenoid, centered on and perpendicular to the solenoid axis, is A) . B) . C) μ0πa2nI. D) 2μ0πa2nI. E) 0. .
C) μ0πa2nI.
D) 2μ0πa2nI.
E) 0.

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A segment of wire of total length 3.0 m carries a 15-A current and is formed into a semicircle. Determine the magnitude of the magnetic field at the center of the circle along which the wire is placed.


A) 1.6 μT
B) 4.9 μT
C) 1.0 μT
D) 9.8 μT
E) 15 μT

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A 0.50-m long solenoid consists of 1000 turns of copper wire wound with a 4.0-cm radius. When the current in the solenoid is 18 A, the magnetic field at a point 1.0 cm from the central axis of the solenoid is


A) 0.090 mT.
B) 0.36 mT.
C) 23 mT.
D) 36 mT.
E) 45 mT.

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Three long, straight, parallel wires all lie in the yz plane and each carries a current of 20 A in the positive z direction. The two outer wires are each 4.0 cm from the center wire. What is the magnitude of the magnetic force on a 50-cm length of either of the outer wires?


A) 1.0 mN
B) 0.50 mN
C) 1.1 mN
D) 1.5 mN
E) 2.0 mN

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Two parallel and coaxial current loops of radius a are placed a distance 2L apart. The current in each ring circulates in the same direction. At a point on the axis half way between the loops the magnetic field in T has magnitude


A) 0.
B) Two parallel and coaxial current loops of radius a are placed a distance 2L apart. The current in each ring circulates in the same direction. At a point on the axis half way between the loops the magnetic field in T has magnitude A) 0. B) . C) . D) . E) . .
C) Two parallel and coaxial current loops of radius a are placed a distance 2L apart. The current in each ring circulates in the same direction. At a point on the axis half way between the loops the magnetic field in T has magnitude A) 0. B) . C) . D) . E) . .
D) Two parallel and coaxial current loops of radius a are placed a distance 2L apart. The current in each ring circulates in the same direction. At a point on the axis half way between the loops the magnetic field in T has magnitude A) 0. B) . C) . D) . E) . .
E) Two parallel and coaxial current loops of radius a are placed a distance 2L apart. The current in each ring circulates in the same direction. At a point on the axis half way between the loops the magnetic field in T has magnitude A) 0. B) . C) . D) . E) . .

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The segment of wire (total length including portions of incoming and outgoing wire = 6R) is formed into the shape shown and carries a current I. What is the magnitude of the resulting magnetic field at the point P? The segment of wire (total length including portions of incoming and outgoing wire = 6R) is formed into the shape shown and carries a current I. What is the magnitude of the resulting magnetic field at the point P? A) B) C) D) E)


A) The segment of wire (total length including portions of incoming and outgoing wire = 6R) is formed into the shape shown and carries a current I. What is the magnitude of the resulting magnetic field at the point P? A) B) C) D) E)
B) The segment of wire (total length including portions of incoming and outgoing wire = 6R) is formed into the shape shown and carries a current I. What is the magnitude of the resulting magnetic field at the point P? A) B) C) D) E)
C) The segment of wire (total length including portions of incoming and outgoing wire = 6R) is formed into the shape shown and carries a current I. What is the magnitude of the resulting magnetic field at the point P? A) B) C) D) E)
D) The segment of wire (total length including portions of incoming and outgoing wire = 6R) is formed into the shape shown and carries a current I. What is the magnitude of the resulting magnetic field at the point P? A) B) C) D) E)
E) The segment of wire (total length including portions of incoming and outgoing wire = 6R) is formed into the shape shown and carries a current I. What is the magnitude of the resulting magnetic field at the point P? A) B) C) D) E)

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What is the magnitude of the magnetic field at point P if a = R and b = 2R? What is the magnitude of the magnetic field at point P if a = R and b = 2R? A) B) C) D) E)


A) What is the magnitude of the magnetic field at point P if a = R and b = 2R? A) B) C) D) E)
B) What is the magnitude of the magnetic field at point P if a = R and b = 2R? A) B) C) D) E)
C) What is the magnitude of the magnetic field at point P if a = R and b = 2R? A) B) C) D) E)
D) What is the magnitude of the magnetic field at point P if a = R and b = 2R? A) B) C) D) E)
E) What is the magnitude of the magnetic field at point P if a = R and b = 2R? A) B) C) D) E)

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